Hydraulic brake mechanism for automotive vehicles



Oct. 26 1926.

c. s. BRAGG ET AL HYDRAULIC BRAKE MECHANISM FOR AUTOMOTIVE VEHICLES Filed March 14 1925 3 Sheets-Sheet 1 C veg Oct. 26 1926.

C. S. BRAGG El AL HYDRAULIC BRAKE MECHANISM FOR AUTOMOTIVE VEHICLES .1925 3 Sh'eets-Sheet 2 Filed March g MN QM C 3 Q INVENTQRS R d Oct. 26 1926.

c. s. BRAGG ET AL HYDRAULIC BRAKE MECHANISM FOR AUTOMOTIVE VEHICLES I Filed March 14 1925 3 Sheets-Sheet 3 Q QM mwmzg ATTORNEY Patented a. 26, 1926. l,604,54'5

UNITED' STATES PATENT OFFICE.

CALEB S. BRAGG, OF PALM BEACH, FLORIDA, AND VICTOR W. KLIESRATH, OF PORT WASHINGTON, NEW-YORK, ASSIGNORS T0 BRAGG-KLIESRATH CORPORATION, OF LONG ISLAND CITY, NEW YORK, A CORPORATION OF NEW YORK.

HYDRAULIC BRAKE MECHANISM FOR AUTOMOTIVE VEHICLES.

I Application filed March 14, 1925. Serial No. 15,460.

Our invention coiisists in the novel feaa cylinder and a double acting piston there tures hereinafter described, reference being in, and a controlling valve permitting nor- 55 had to the accompanying drawings, which mally the circulation of the motor fluid illustrate vone embodiment of the same, sethrough the actuator and adapted to regulected by us for purposes of illustration, and late the amount of pressure applied by the the said invention is fully disclosed in the actuator to the brakes, a suit-able reservoir following description and claims. being provided for the motor fluid, and con- 60 Our invention consists in a hydraulic nections therewith, by means of which the brake system for automotive vehicles, adaptpump can be continuously operated to proed especially for the larger types of vehivide the necessary movements of the mocles, such as trucks, busses, and particularly tor fluid without stopping the pump. Our six and eight wheel vehicles in which fluid invention also contemplates means whereoperated brakes adapt themselves more per-' by the operator may add his physical fectly to installation and use. For example, strength to'the power exerted by the power l5 it is a difiicult matter in mechanical brake actuator in the application of the brakes. installations to lead all of the brake rods and also in the event of a partial or to a single control, and maintain equalizacomplete failure of the liquid pressure 4 tion under all road conditions, due to the system. The pump is driven from the varying amount of movements of the indimotor or the vehicle, either directly or in vidual wheels, or pairs of wheels, with rethe latter case through the power transspect to the other wheels, or to the chassis. mission mechanism, and it is obvious, there- This is further complicated by the low fore, that whenever the motor is stopped, frame construction required for passanger or in the latter case, whenever the vehicle is' busses. Itfollows, consequently, thatwhen stopped, the pump would cease to be oper- 5 one wheel, or a pair of wheels drop into a ated, and. there would be no mechanical depression of considerable depth, the brakes power available to kee the brakes applied.

atthat time being fully apphed, the operatif thevehicle were stan ing on a grade with- 'ing device, whether a manually operated out this provision for the direct application pedal or power cylinder, will be retracted by of the physical force of the operator to the '10 the uncompensated increased distance bebrake mechanism. 7

tween the brake applying lever on the drum 1 In the accompanying drawings, which and the chassis and if the brakes are applied illustrate one embodiment of our invention, 87 v by a foot operated lever or pedal, a disagreeselectedby us for purposes of illustration.

able kick being the result. If the brakes are Fig. 1 represents a more or less diagram- 36 partly applied, but not to the maximum exmatic view of a portion of the chassis of an tent, and a wheel or a pair of wheels, falls automotive vehicle and showing our inveninto such a depression, the result would be tionembodied therein; y that the other brakes on the wheels not at Fig. 2 is a diagrammatic view illustrating.

' footed, would be applied with more force the power actuator, the pumpyliquid reser-.

than desired bythe operator, unless the foot voir, and the pipe connections appertaining lever was released. It therefore is desirable theretoz to apply the brakes in heavy automotive ve Fig. 3 represents an enlarged sectional 96 hicles of the type mentioned, through a view of the power actuator illustrated in more flexible means, as by fluid pressure. Figs. 1 and 2.

1:15.45 conducted through hose or flexible metallic Referring to the embodiment of the invenhydraulic tubing, and we refer. toemploy tion illustrated in theaccompanying drawa li uid, and preferably hilt/and to operate ings, we have shown in Fig. 1, in a diagram-11o!) the rakes by meansof a power actuator matic manner, an installation embodying a under thecontrol of an operator operated our invention, and arranged for the alplvpeliw s 50 lever, or pedal. Our invention, therefore, cation of brakes to each of the four consists o a hydraulic brake system 00111 of a four wheeljvehicle, it being upderstood H prising a. mech pump, an acthat by extending the pipe connections from 10! tuator therewith, and including the actuator, as hereinafter explained, any

desired number of hydraulic brake applylngcylinders may be operated for the simultaneous application of brakes to any desired number of wheels, with which the vehicle may be provided, as six, eight, etc, and by providing the necessary flexible connections, brakes on the wheels of a trailing vehicle can in like manner be applied and released simultaneously with the brakes of the main vehicle. In Fig. 1, 1, represents the chassis of an automotive vehicle, provided with brake mechanism. indicated diagrammatically at 2, and 3, for the forward wheels, and also brake mechanism, indicated diagrammtically at 4 and 5, for the rear wheels, said brake mechanisms being independent, and the brake mechanism for each wheel being provided with a suitable hydraulic cylinder and piston for applying and releasing the same, said cylinders being indicated diagrammatically at 2, 3 4 and 5. The particular type of brake mechanism and the hydraulic cylinder and piston for actuating the same. maybe of any usual and de-' sired construction, and as their .specific de tails form no part of our present invention, they will not be specifically described. 6 represents the cylinder of our improved power actuator, shown in detail in Fig. 3, which is closed at its opposite ends by the heads, 7 and 8, connected by the bolts, 9,. and nuts, 10, and within the cylinder, 6, is a double acting piston, indicated at 11, provided with gaskets, 12, having oppositely disposed portions. The hub of the piston is provided with a hollow piston rod, indicated at 13, extending through a stifling box,

14, provided with a packing sleeve 15, preferably of rubber, held in place by a follower, 16. The hub of the piston is preferably provided with a central chamber, indicated at 17, having valve seats, 18 and 19, at its opposite ends, and a longitudinally movable valve actuating sleeve, 20, extends through the hub of the piston and other end of cylinder. which is provided with a'stuifing box, 21, packing sleeve, 22, and follower, .23, said sleeve also passing through the hub of the piston and into the hollow piston rod, which it fits and with which it has a sliding engagement. In order to prevent leakage- OI oil from one side of the piston to the other around the sleeve, we prefer to provide the piston hub also with a stufiing box, indicated at 24, and having a packing sleeve. 25, and follower, 26., for example, for effecting a tight joint between the sleeve and piston. The packing sleeves, 15, 22 an ll 25, are all preferably constructed of rubber and provided with sleeve'portions fitting the part passing therethrough and with flange. portions to be engaged by the follower, to clamp it box recess, the sleeve portions ing slightly smaller than the said recess, the packing sleeves arranged so that any leakage of oil into the recess will accumulate pressure exterior to the sleeve portion of the packing and cause it to be compressed upon the part passing therethrough, so as to maintain the joints as tight as possible and prevent leakage.

The sleeve, 20, is provided internally with a plug or partition, indicated at 27, and said sleeve is provided; in rear of said partition (to the right in Fig. 3) with inlet apertures, 28, adapted to communicate with the chamber, 17, in the piston. The sleeve, isalso provided, forward of the partition, 27 (to the left in Fig. 3) with outlet apertures, indicated at 29. also adapted to communicate with the chamber, 17. Within the chamber, 5

17. the sleeve is provided with two valves, indicated respectively at 30 and 31, for engaging, respectively the valve seats, 18 and 19. These valves may beformed as shown,

in a single valve member secured to the sleeve by spring rings, indicated at 32, or otherwise, or the valves may be separate and separately connected with the sleeve, if preferred' The exterior portion of the sleeve, 20, is provided with means for connecting it with a suction or outlet'pip'e, indicated at 33-, and also with means for connecting it with an operator operated device. In this instance we have shown the outer end of the sleeve, 20, provided with a fitting,34, having an interior chamber communicating with the interior of the valve sleeve, and a nipple, 35, secured to the pipe, 33, said fitting being also provided with a perforated lug, or lugs, 36.which are connected by a link member, 37, with the usual brake lever or pedal lever, 38, provided with foot engaging portion, 39, as indicated in Fig. 1. The exterior portion of the sleeve, 20, is also'provided with means for arresting it in such position, when the piston isin its normal or off position, at

gagement with the head, 8, of the actuator cylinder, the valves, 30 and 31. will be maintained in open position. and thus provide a by-pass from the apertures. 28, completely around the partition, 27, through the chamber, 17 to apertures, 29, for by-passing the motor fluid from the rear end of the sleeve, 20. to the forward end thereof, and to ,permit of a circulation of the motor fluid, as hereinafter explained. In this instance we have shown a stop collar. indicated at 40, on the sleeve, 20, adapted to strike against the adjacent end of the follower, 23, when the parts are in normal or off position, so as to.

arrest the sleeve in a position to hold both valvesopen. This collar may be adjusted on the sleeve, 20, and locked on any desired position, by a set screw, or otherwise, if such adjustment is/necessary to secure this result.

Instead of providing the pedal lever, 38, with the usual retracting spring for retracting the pedal lever and valve actuating sleeve connected therewith, we prefer to locate the retracting spring between a part connected with the sleeve, 20, and a part connected with the piston, in order that the pressure upon the foot lever required for the purpose of overcoming the retracting spring may be directly applied to the piston in a direction to apply the brake mechanism, and thus be T and the oil may be handled. by the gear type utilized instead of being wasted. as is the case where the retracting spring is applied directly to the pedal lever. In this instance we have .shown the valve actuating sleeve, 20, provided with a hollow extension or tube, provided with a collar, 41, threaded, and a retracting spring 42 .is located within a recessed portion of the hollow piston, 13,

K and surrounding the sleeve extension, 20*,

and engaging a shoulder on the interior of the piston rod, in this instance a washer, 43. being interposed between said shoulder and the spring. The outer end of the hollow piston rod is shown as provided with a hollow fitting, 44, having a lateral connection, 45,

. to which an inlet pipe, 46, for motor fiuid is connected, and the sleeve extension, 20*, is provided with a plurality of apertures, 20, to permit the motor fluid-to enter the interior'of the sleeve extension, 20, and sleeve, 20, and pass through the inlet apertures, 28. In order to maintain the sleeve in a balanced; condition'so that its rearward movement will not be impeded by the pressure of the motor fluid when the brakes are fully applied, we prefer to provide the rear end of the sleeve extension, 20 with a small. pressure equalizing piston, indicated at 47 which in this instance is located within the fitting, 44, and

v in rear of (to the right in Fig. 3) the connection, 45, the outer end of the fitting, 44, being provided with an aperture, 48, communicating with the atmosphere to prevent the compression of air or accumulation of oil within said fitting, which might inter-.

fere with the free operation of the sleeve.

The equalizing piston 15 not, however, abso-- lutely necessary, but lessens theload which otherwise would have to beovercome by the operators foot, in order to overcome the retracting spring if it were made sufficiently strong to operate the valves against the full oil pressure to release the brakes. The piston, 11, is provided with aport, or ports, indicated at 49, connecting the-chamber, 17, with the cylinder on the rear side of the piston (to the right in Fig. 3) There is no connection, however,' between the portions of the cylinder on opposite sides of the piston (except as hereinafter explained),- the portion of the cylinder on the forward side of the piston being filled with motor fluid and connected by a pipe, 50, with the several brake applying c linders (as 2, 4. and 5) through suita le branch pipes, indicated at 5'1. 7'

Referring now to Figs. 1 and 2, we

describe the system of pipe connections for effecting the proper movements of the motor liquid. Any suitable motor fluid may be employed in connection with our improved actuator, but we prefer to use an incompressible liquid, as oil, which offers the advantages that smaller cylinders may be employed for applying the individual brakes,

hydraulic pump, which is simpler in construction and operation than the reciprocating air pump, and further, there is less piping and less storage tank space required where a liquid such as oil is used. We prefer to employ castor oil as the motor liquid, particularly on account of the fact that we prefer to use rubber for packings, which is not affected injuriously by castor oil. We wish it to be understood, however, that we may use other kinds of packing'and other oil than castor oil, if preferred. As best shown in Fig. 2, 52, represents theoil circulating pump, which is of the ordinary gear type of hydraulic pump, but which may be of any other desired construction, and is provided with a driving shaft, indicated at 53, which is driven in any preferred manner, either from the engine which propels the automotive vehicle, or from the power transmission valve sleeve. The intake or suction pipe, 54, c

of the pump is also connected with an oil reservoir, indicated at, 57, b an intake pipe,

58, in which is located a c eck valve, indicated at 59, opening in thedirectipn of the arrow in Fig. 2, and preferably provided with a spring, set or ca ibrated to approximately the equivalent of atmospheric pressure, for example, twelve to thirteen pounds per square inch. The intake pipe, 58, is also provided preferably, though not necessarily, with a by-pass pipe, 60, connected to the pipe, 58, on opposite sides of the checkvalve, 59, the pipe, 60, being provided with a check valve, 61, havin no spring, and opening in the op e ite 'rection from the check valve, 59, as Indicated by the arrows in Fig. 2. On the pressureside of the pum' it is cpnnected by a main pipe, 62, having e ible portion, 46, with the :inlet connection, 45, on the hollow piston rod communicating, as before described, with the interior of the valve actuating sleeve, 20, in rear of the partition, 27. The pipe, 62, is also connected -with the tank or reservoir, 57 b a pipe, 63,

check valve, 67 opening in the opposite direction, as indicated by the arrow Fig. 2, and provided with a spring normally holding the check valve closed, with a pressure of approximately the maximum pressure desired in the system, as, say, eighty pounds, for example.

closes the valve, 31, upon its seat, and shuts offthe outlet for the normal constantly cir-. culat-ing stream of oil, and instantly builds up a pressure which forces the oil to enter the cylinder in rear of the piston through the ports, 49, and forces the piston ahead. 'lheforward movement of the piston forces It being understood that the actuator is in the oil contained, in the cylinder forward "itsnormal or oii' position, in which Il1"plS"til1T9Qf,Ol1ll through the pipe,-. 50, and its ton is at the rear end of the cylinder (at the branch pipes, 51, to the various brake applyright in Fig. 3) and that the valve actuating ing cylinders, as 2, 3*, 4 and 5, for exsleeve, 20, has been brought to rest under the ample, operating the pistons therein, which action of the retracting spring,'42 *with*its arewonnected to the brake bands, or shoes, stop collar, 40, in engagement with the folin any usual or desired manner, and applylower, 23, so as to hold the valves, 30 and 31, ing the brakes. \Vhen the operator stops in open position, and the entire pipe systhe-forward movement or" his foot, the prestern hereinbefore described being filled with sure behind the piston will cause its forward oil or other motor fluid, as well as the resmovement to continue until the piston has ervoir, 57, if the pump is started, it will he been moved forward with respect to the seen that the oil will freely circulate from valve sleeve, sgfiiciently to open the valve, the pump through the pipes, 62- and 46, 31, to such an extent as to by-pass just sufiithrough the sleeve and piston, and through cient quantities of oil to maintain the rethe pipes, 56, 55 and 54, back to the pump. quire-d amount of pressure -in rear of the This is especially desirable and important, piston to hold it against theload of the as the conventional'type of gear pump must brake mechanism, in a balanced. position. be kept constantly primed iii" instantaneous It will be noted that when the maximum pressures are to be obtained from it, as is pressure of the oil pump has been exerted both desirable and necessary in the operaon the actuator pistonQt-he operator may, by tion of brake mechanism. 1t would, therefurther depressing the brake level, or pedal fore, be unwise to shut oil the outlet from lever, add his physical force to further apthe pump, which would increase the necesply the brakes, as the relative movement, or sary power required to drive it when the i lost motion,h'ctwcen the slceve.'20, and the a, brake mechanism was not in use, and consepiston is limited, in this instance by the enquently cause more wear and more pressure gagement of the respective valves, 31 and 30, with the resulting dan ers of failure of opwith their seats. eration and leakage. n the other hand, it however, be limited in other ways,'if desired. is unwise to cut off the intake to the pump, lVhen the brakes are applied, the valve,31,

, as the interval between the intake valve and being closed, no oil can be withdrawn from the time when the pump picks up its primthe actuator through the pipes, 56 and 55, ing and delivers its full power, requires a and the pump will receive its oil from the varying period of time which would delay reservoir, 57, and force the same through the application of the brake mechanism, and pipes, 62 and 46, into the actuator in rear of furthermore, the suction which would be crethe piston, and when the forward movement ated by cutting off the intake would tend to of the valve actuating sleeve, 20, ceases. and suck the air into the gears, in case there were the valve, 31, is normally opened, as before This lost motion may,.

any leaks in the system resulting in the described, the circulation of the oil through pumpbecoming air bound and failing to opthe normal circulating system, represented erate for a considerable length of time after by pipes, 62, 46, to the actuator and pipes, the opening of such a valve.. Our construc- 56, 55 and 54, from the actuator, will be retion avoids all of these difliculties and persume d. When the operator removes hisfoot mits the continous operation of the pump from the brake pedal, the retracting spring when the actuator and brake mechanism are ,will cause the valve sleeve to move rearnot m use, by freely-circulating the mowardly, or in a direction opposite that'of tor liquid through the actuator in the manthe arrow in Fig. 3, thereby closing the i2" ner described. valv e, 3 0, and permitting the pump to with- When the operator applies lllS foot to the draw oil from the cylinder in rear of the brake pedal, the valve sleeve is moved forpiston, through the passage, 49, the actuatward, thereby cpmpressing the retractioning valve sleeve, 20,'/and pipes, 56, 55 and spring, 42, sufiiciently to permit the valve 54. As no further'oil can be pumped into sleeve to be moved in the direction of the the actuator from the pipe, 62, the oil, on

arrow, Fig. 3, with respect to the plston, leaving the pump, will pass through the the physical force of the operator applied spring actuated check. valve, 67, to the reserto the foot lever for thepurpose of pressing voir, thus withdrawing the surplus oil withthis spring being transmitted to the piston drawn from the reservoir to effect the actualn a direction to apply the brakes.'- ThlS tion of theactuator, and causing the piston w in closed position, is set to the desired operating pressure, as before stated, which must be less than the normal pressure of the pump,

in order to provide an outlet for the oil,

which is Withdrawnfrom the actuator to return the piston to, or towards, normal position. The check valve, 59, is, as before stated, provided W-itha spring exerting a pressure of approximately atmospheric pressure, tending to hold it closed, so that on the closing of the valve, 30, the pump will suck the oil out of the actuator and effect the retracting action, up to approximately atmospheric pressure, instead of drawing oil from thereservoir, and thus return the piston to or toward its normal position. Our improved construction also provides means by which the brakes may be applied by the physical power of the operator, for example, when the pump is not in operation; Assuming that the pump is not running, the operator may, by applying his physical power to the. foot lever, move the valve sleeve, 20, forward so as to close the valve,

31, and thereafter positively move thepiston forward, the necessary oil required'to keep the cylinder in rear of the piston filled being supplied from the reservoir, 57, through the check valve, 66, and flowing therethr-ough in the direction of the arrow, Fig. 2. As the piston moves forward, the pressure exerted thereon by the operator, will be transmitted to the oil forward of the piston. and

throughthe pipes and 51, t0 the several brake applying cylinders connected .therewith. When -the foot lever.is released, the

' valve sleeve will be shifted by the retracting spring, 42, so as to close the valve, 30, leaving the valve, 31, open and the load of the applied brakeswill tend to return oil from the brake applying cylinders through pipes, 51 and 50, to the forward side of the piston and move the piston rearwardly, the oil within the actuator in rear of the piston passing out through the pipes, 56 and 55, and passing through the pipes,58, and bypass, 60, and through-the check valve, 61;

'in the direction of the arrow, back to the reservoir.

The by-pass, 60, and check valve, 61, are unnecessary if theoil pump is operated by thev motor, as the oil could be withdrawn from'the actuator as soon as the motor-was started, when itwas desired to release the brakes, and unless the motor were started,

vehicles of this size could not be conveniently moved. However, when the oil pump is driven from the transmission members connected to the rear wheels and not to the motor, the oil could not be withdrawn from the cylinder to release the brakes until the vehicle was actually in motion, unless the bypass, 60, and check valve, 61, were provided, and this in most cases would be objectionable. We, therefore, prefer to provide such a by-pass and check valve where the pump is driven from the transmission mechanism, and it may be provided in all installations, if desiredr It will be noted that the actuator herein shown and described performs two important functions. The piston divides the cylinder into two entirely separate chambers, having no connection with each other except as hereinafter noted. One of these chambers, on one side of the piston, which may be termed the service chamber, is connected with the brake applying cylinders. The other of said chambers, on the other side of the piston, which may be termed theactuator chamber, is connected with the source of pressure fluid admitted to and discharged therefrom under the control of the valve -mechanism, the movements of the piston produced by the accumulation of pressure or release of pressure in the actuator chamber (or by the physical force exerted by the operator) effecting the application or release of the brakes, thus simplifying the apparatus and dispensing with a special pressure cylinder and piston.

lVhen it is not essential to the operation of our improved apparatus, we prefer to in some instances provide means for replenishing the oil in the pressure system connected with the brake applying cylinders to supply a deficit which may be caused by leakage, or by a break in the piping, for example- For this purpose, in some instances, we may provi'de the piston. with a passage which may be in the form of an aperture, 7Q, or a by-pass, connecting the servicechamber of the actua tor with the actuator chamber, thereof, which aperture is provided with a check valve, '71, opening in the direction of the service chamber, but normally held closed by a spring, 7 2.

When the brakes are to be applied and pressure is. accumulated in the actuator piston, a substantially equal pressure willexist in the servicecha mber on the opposite side ofthe piston, and the valve, 71, will remain closed. When the pressure of the operators foot is applied to the piston the pressure in the service chamber will be greater than in the actuator chamber, and the valve, 71-, will be held closed. If there is a leak in the service pipes, however, or a break therein, so

that an escape of oil takes place, the pressure.

in the actuator'chalhber when the actuator is operated to the full extent, and in such case, or when for any reason the pressure in the service chamber is less than that in the actuator chamber, the oil will pass through the aperture (or by-pass) '70, and open the valve,

71;, and bring the pressure in the service pipes up to that inthe actuator chamber, so as to insure'the proper operation of the brake applying pistons.

v compensated for in the main circulating sys? torn from. the oil reservoir. As before stated the aperture (or by-pass) 70 and valve 71 may be omitted, if desired.

What we claim and desire to secure by Letters Patent is 1. In a hydraulic brake system, a power actuator com rising a cylinder closed at both ends, a piston in said cylinder dividing it lnto a service chamber at one slde or the plston, and an actuator chamber separate therefrom on the other side of the piston,

said service chamber being provided with a liquid passage tor'counecting it to a hydraulic brake actuating cylinder, and said actuator chamber being provided with liquid both ends, a piston in said cylinder dividing it into a service chamber at one side of the piston, and an actuator chamber separate therefrom on the other side of the piston, said service chamber being provided witha liquid passage for connecting it to a hydraulic brake actuating cylinder, and said 1 actuator chamber being provided with liquid connections for admitting motor liquid to and discharging it from said chamberq/and valve mechanism for controlling the said connect ons from said actuator chamber, an operator operated part for controlling said I valve mechanism, operatively connected with the piston by means permitting lost motion,

wherebythe physical power of the operator may loo-applied to the piston in a direction to apply the brakesin addition to the powerof the actuator or in case the actuator is inoperative.

3. In a hydraulic brake system, a poweractuator comprising a. cylinder closed at both ends, a piston in said cylinder dividing it into a-service chamber at one side of the piston, and an actuator chamber separate there'- from on the other side of the piston, said service chamber being provided with a liquid passage for connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a connection from thepressureside of said pump to said actuator chamber, a connect on from the suction side of said pump to said actuator chamber, valve mech- The' oil will be accuses anism for controlling said connections, and

an operator oplerated device for controlling from on the other side of the piston, said service chamber being provided with a liq- -uid passage for connecting ity to a hydraulic bra-keactuating cylinder, a liquid pressure pump, a connection from the pressure'side of-said pump to said actuator chamber, a connection from the suction side of said pump to said actuator chamber, valves for controlling said connections, and an operator operated device connected with said valves, and capable of holding said valves in open position to permit'a continuous circulation of liquid through said connections and to close one or other of said valves to efi'ect a delivery of pressureliquid into, or a discharge of pressure liquid from said actuator chamber. i

'5. In a hydraulic brake system, a power actuator comprising a cylinder closed at both ends, a piston in said cylinder dividing it into a servicechamber at one side of the piston, and an actuator chamber separate therefrom on the other side of the piston, said service chamber being provided with ,a liquid passage for connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a connection from the pressure side of said pump to said actuator chamber, a

connection from the suction side of said pump to said actuator chamber, valves for controlling said connections, a valve actuating device connected with said valves, and

constructed to hold them in open position to permit a continuous circulation of liquid through said connections and to close either of said valves to'efiect a delivery of'pressure liquid to or a discharge of pressure liquid from said actuator chamber, an operator operated deviceconnected with said valve actuating device, and means for arresting said-valves in open position when the piston is in thc,normal or oil position.

6. In a hydraulic brake system, a power actuator'comprising a cylinder closed at both ends, a piston in said cylinder dividing it into aservice chamber at one side of the piston, and anactuator chamber separate therefrom on the other side of the piston, said service chamber being provided with a liquid passage tor connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a connection from the pressure side of said pump to said. actuator chamber, a

connectionwiromflthe nsuctionwside of a said pump to said actuator chamber, valves for controlling said connections, a valve actuating device connected with said valves, and

constructed to hold them in open position to permit a continuous circulation of liquid through said connections and to close either of said valves to effect a delivery of pressure liquid to or a discharge of pressure liquid from said actuator chamber, an operator operated device connected with said valve actuating device, and means for arresting said valves in open position when the piston is in the normal or off position, said valve actuating device being operatively connected with the piston by means permitting sutficient lost motion to effect the closing of either of said valves, whereby the piston may be actuated by the operator to add his physical force to the power of the actuator, or in case the source of power fails.

7 In a hydraulic brake system, a power actuator comprising a cylinder closed at both ends, a piston in said cylinder dividing it into a service chamber at one side of the piston, and an actuator chamber separate therefrom on the other side of the piston, said service chamber being providedwith a liquid passage for connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a connection from the pressure side of said pump to said actuator chamber, a connection from the suction side of said pump to said actuator chamber, valves for controlling said connections, and an operator operated device connected with said valves, and capable of holding said valves in open position to permit a continuous circulation of liquid through said connections, and to close one or other of said valves to effect a delivery of pressure liquid into or a discharge of presure liquid from said actuator chamber, and a liquid reservoir, operatively connected with said pump, on the suction side, for supplying the pump, when the suction connection with said actuator chamber is closed. 7 Y

8. In a hydraulic brake system, a power actuator comprising a cylinder closed at both ends, a-piston in said cylinder dividing'it into a service chamber at one side of the piston, and an actuator chamber separate therefrom on the other side of the piston, said service chamber being provided with a liquid passage for connecting it to a hydraulic brake actuating, cylinder, a liquid pres-' sure pump, a connection from the pressure slde of said pump to sald actuator chamber, a connection from the suction side of said pump to said actuator chamber, valves for controlling said connections, and an operator operated device connected with said valves, and capable of holding said valves in open position to permit a continuous circulatlon oi liquid through said connections, and to close one or other of said valves to effect a delivery of pressure liquid into, or a dis- 'charge of pressure liquid from said actuator chamber, a liquid reservoir, operatively connected with said pump, on the suction side, for supplying the pump, when the suction connection with said actuator chamber is closed, a check valve for said reservoir connection, and a spring for holding said check valve closed to insure the withdrawal of liquid from the actuator chamber when the suction connection of the pump therewith is open.

9. In ahydraulic brake system, a power actuator comprising a cylinder closed at both ends, a piston in said cylinder dividing it into a service chamber at one side of the piston, and an actuator chamber separate therefrom on the other side of the piston, said service chamber being provided with a liquid passage for connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a connection from the pressure side of said pump to said actuator chamber, a connection from the suction side of said pump to said actuator chamber, valves for controlling said connections, an operator operated device connected with said valves, and capable of holding said valves in open position to permit a continuous circulation of liquid through said connections, and to close one or other of said valves to effect a delivery of pressure liquid into, or a discharge of pressure liquid from said actuator chamber, a liquid reservoir, a connection therefrom to the suction side of the pump for supplying the pump when the suction connection with the actuator chamher is closed, a connection from the reservoir to the pressure side of the pump to permit the pump to discharge liquid into said reservoir when the connection from the pump to the actuator is closed, and automatic valves controlling said reservoir connections.

' 10. In a hydraulic brake'system, a power actuator comprising a cylinder closed at both ends, a piston in said cylinder dividing it into a service chamber at one side of the piston, and an actuator chamber separate therefrom on the other side of the piston, said service chamber being provided with a liquid passage for connecting it to a hydraulic v brake actuating cylinder, a liquid pressure pump, a connection from the pressure side of said pump to said actuator chamber a connection from the suction side of said pump to said actuator chamber, valves for controlling said connections, an operator operated device connected with 'said valves, and capable of holding said valves in open position in said connection, a spring holding said check valve closed with a pressure approximately equal to atmospheric pressure, aconnection from the reservoir to the pressure side of the pump, a check valve controlling said connection, and a spring for said check valve normally holding it closed with a predetermined pressure, not exceeding the pressure which the pump is capable of producing.

11. In a hydraulic brake system, a power actuator comprising a cylinder closed at both ends, a piston in said cylinder dividing it into a service chamber at one side of the piston, and an actuator chamber separate therefrom on the other side of the piston, said service chamber being provided with a liquid passage for connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a connection from the pressure side oi said pump to said actuator chamber, a connection from the suction side of said pump tolsaid actuator chamber, valves for controlling said connections, an operator operated device connected with said valves, and capable of holding said valves in open position to permit a continuous circulation of liquid through said connections, and to close one or other oil said valves to elicct a de livery of pressure liquid into, or a discharge of pressure liquid from said actuator chamber, said operator operated device being conneoaueb actuator comprising a cylinder closed at both ends, a piston in said cylinder dividing it into a service chamber at one side of the piston, and an actuator chamber separate therefront on the other side of the piston, said service chamber being provided with a liquid passage for connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a connection from the sure side of said pump to said actuator c amber, a connection from the suction side of said pump to said actuator chamber, valves for controlling said connections, an operator operated device connected with said valves, and capable of holding said valves in open position to permit a continuous circulation of liquid through said connections, and to close one or other of said valves to effect a dereslivery of pressure liquio into, or a discharge of pressure liquid from said actuator chamher, a liquid reservoir, an auuiliary suction "i i es bxia ans panacea 'lost'motion, a l1qu1d reservoir, a connection from said reservoir to said actuator chamber, for-supplying liquid thereto when the piston is actuated by the operator operated device, and a check valve in said connection.

'12. In a hydraulic brake system, a power actuator comprising a cylinder closed at both ends, a piston in said cylinder dividing it into a service chamber at one side of the piston, and an actuator chamber separate therefrom on the other side of the piston, said service chamber being provided with a liquid passage for connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a. connection from the ressure side of said pumptosaid actuator c amber, a connection fromithe suction side of. said pump to said actuator chamber, valves for controlling said connections, an openator operated device connected with said valves, and capable -oi holding said valves in'open position to permit a continuous circulation of liquid through said connections, and to close-one or other of said valves to effect a delivery of pressure liquid into, or

vice being connected with the piston by means'permitting lost motion, a liquid reservoir, connections from the reservoir to tie pump on the suction side and pressure side ated valve 111 saidauxihary suction connection for preventing the Withdrawal of liquid from the reservoir when the suction connection from the pumpto the actuator is open, a icy-pass around said spring actuated valve,

and an auxiliary check valve in said bypass opening in the opposite direction from the said spring actuated valve.

14. In a hydraulic brake system, a power actuator comprising a cylinder closed at both ends, a piston in said cylinder dividing it into a service chamber at one side of the piston, and an actuator chamber separate therefrom on the other side of thepiston, said service chamber being provided with a' liquid passage for connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a connection from the pressure side of said pump to said actuator chamber, a connection from the suction side of saidpump to said actuator chamber, valves for controlling said connections, an operator operated device connected with said valves, and capable of holding said valves in open position to permit a continuous circulation of liquid through said connections, and to close one or other of said valves to efiect a delivery of pressure liquid into, or a discharge of pressure liquid from said actuator chamber, a liquid reservoir, an auxiliary suction connection therefrom to the-suction side of the pump, for supplying the pump when the suction connection, from the actuator chamber is closed, a normally closed spring actuated valve in said auxiliary suction connection, a by-pass around said spring actuated valve, and an auxiliary check valve in said by-pass opening in the opposite direction from the said spring actuated valve, a connection from the reservoir to the pump on the pressure side thereof, and a check valve in said connection normally held closed by a spring of redetermined pressure.

15. In a hy raulic brake system, a power actuator comprising a cylinder closed at both' ends, a piston in said cylinder dividing it into a service chamber at one side of the piston, and an actuator chamber separate therefrom on the other side of the piston, said service chamber being provided with a liquid passage for connecting it to a hydraulic brake actuating cylinder, a liquid pressure pump, a connection from the pres sure'side of said pump to said actuator chamher, a connection from the suction side of said pump to said actuator-chamber, valves for controlling said connections, an opera tor operated device connected with said valves, and capableof holding said valves in open position to permit a continuous circulation of liquid through said connections, and to close one or other of said valves to efiect a delivery of pressure liquid into, or a discharge of pressure liquid from said actuator chamber, a liquid reservoir, an auxiliary suction connection therefrom to thesuction side of the pump, for supplying, the pump when the suction connection from the actuator chamber is closed, a main check valve in said auxiliary suction connection, a

by-pass around said check valve, and an auxiliary check valve in said by-pass opening in the opposite direction from the said main check valve, said main check valve being normally held closed by a spring of pre determined pressure, to prevent the withdrawal ofliquid from the reservoir when the suction connection from the pump to the actuator is open, a connection from said reservoir to the pump on the pressure side, a

check valve for said connection normally held closed by a spring of predetermined pressure, said operator operated part being connected to the piston by means permitting lost motion, a connection from said reservoir to the actuator chamber to supply liquid ends, a piston in said cylinder dividing it thereto when the piston is moved by said operator operated part, and a check valve ,in said connection to prevent the return of liquid through said connection to the reservoir.

16. In a hydraulic brake system, an actuator comprising a cylinder, closed at both into a service chamber, and a separate actuator chamber, a valve chamber in said piston, connected with the actuator chamber, means for supplying liquid to and withdrawing it from the valve, a valve actuating nected with said valve sleeve, said sleeve being connected with the piston by means permitting lost motion.

17. In a hydraulic brake system, an actuator comprising a cylinder, closed-at both ends, a piston in said cylinder dividingit into a service chamber; and a separate actuator chamber, a valve chamber in said pis ton, connected with the actuator chamber, means for supplying liquid to and withdrawing it from the valve, a valve actuating sleeve extending through said cylinder piston and said valve chamber, and provided withseparated inlet and outlet passages adapted to communicate with said valve chamber, valves carried by said valve sleeve for disconnecting said valve chamber from said passages, means for connecting said service chamber withabrake applying cylinderfand an operator operated device connected with said valve s'leeve, said sleeve being connected with the piston by means permitting lost motion, and a retracting spring interposed between said sleeve and said piston, whereby pressure applied to the operator operated device to move the valve sleeve in the direction to apply the brakes will be transmitted by said spring to the piston and to the brake a plying cylinder.

18. In a h raulic brake system, an actuator comprising a cylinder, closed at both ends, a piston in said cylinder dividing it into a service chamber, and a separate actuator chamber, a valve chamber in said iston, connected with the actuator cham er, means for supplying liquid to and withdrawing it from the valve, a valve actuating sleeve extendingjthrough said cylinder. ,piston and said valve chamber, and provided with separated inlet and outlet passages adapted to communicate with said valve chamber, valves carried by said valve sleeve for disconnecting said valve chamber from said passages, means for connecting said service chamber with a brake applying cylinder, and an operator operated device connected with said valve sleeve, said sleeve being connected with the piston by means permitting lost motion, and a retracting spring interposed between said sleeve and said piston, whereby pressure appiled to the operator operated device to move the valve sleeve in the direction to apply the brakes will be transmitted by said spring to the pistonand to the brake applying cylinder,

and a pressure fluid equalizing piston connected with said sleeve, and working in a cylindrical partw r 19. In a-hydraulic brake system, the combination with an actuator comprising a cylindcr, closed at both ends, a piston therein dividing the cylinder into a service cham her, and a separate actuator chamber, a valve chamber in sald piston communicating withv sa d actuator chamber, a

valve actuating sleeve. extending'through ,7

' ried by, the said sleeve for controlling. said inlet and outlet passages, and means ion holding said valve sleeve in position to maintain both of said valves in open position, and permit a continuous circulation of liquid by-said pump through said valve chamber when the piston is in normal or ofi position. 20. In a hydraulic brake system, the combination with an actuator comprlsing a cyl- .vinder, closed at both ends, a piston therein dividing the cylinder into a service chambegand a separate actuator chamber, a valve chamber in said piston communicating with said actuator chamber, a valve actuatin sleeve extending through said cylinder and piston and said valve chamber, and provided with separated inlet and outlet passages, adapted to communicate with said valve chamber, a pump, a connection from the pressure side of said pump to said inlet passage, a connection from said outlet passage to the suction side of the pump, a connection from the service chamber to a brake actuating cylinder, valves carried by the said sleeve for controlling said inlet and outlet passages, and-means for holding said valve sleeve in position to maintain both of said "valves in open position, and permit a con-' ilfiliOllSUilG'lllfi-ilflil of liquid by said pump through said valve chamber when the piston is in normal or ofi position, saidsleeve being -.connected with the piston by means permitting lost mot-ion, a liquid reservoir, opera tively connectedwith the: pump, spring actuated check-valves controlling said conned j'lous, a separate connection from the reservoir to said actu ator chamber, and a check valve controllingsaid connection.

21,1 a hydraulic brakesystem, a power actuator comprisin a cylinder closed at both ends, a piston in said cylinder 'dividin'g' it into a service chamber at one side of thepiston, and an' actuator chamber separate ther'efrqm on-the other sldeof the iston,

said'service chamber being provid with liquid passages for connecting it to a by draulic brake actuating cylinder, and said actuator chamber being provided with liquid connections for admitting motorliquid to and discharging it from said chamber, and valve mechanism for controlling the said connections from said actuator chamber, said actuator being provided with a passage for establishing communication between the service chamber and the actuator chamber, and arnormallyrclosedr valve for V controlling said chamber, constructed to be opened when the pressure in the actuator chamber exceeds that in the service chamber to supply additional liquid to the service chamber and its connections.

22. In a hydraulic brake system, a power actuator comprising a cylinder closed at both ends, a piston'in said cylinder dividing it into a service chamber at one side of the 'piston, "andan actuator chamber separate valves for controlling said connections, an

operator operated device connected with said valves, and capable of holding said valves in a open positionto permit a continuous circulation of liquid through said connections, and to close one or other of said valves to efiect a'delivery of pressure liquid into, ,or a discharge of pressure liquid 'irom'said actuator chamber, a liquid reservoir, a connection therefrom to the suction side ofthe pump for supplying the pump when the suction connect1on with the actuator chamber is closed, a connection from the reservoir to-the pressure side of the pump to permit the pump to discharge liquid into said reservoir when the connection from the pump to the 119 that in the service chamber to supply addiv vtionalliquid to the service chamber and its connections.

- 23,"; In a hydraulic brake system, a power actuator comprising a cylinder closed at both e s i= decade"ss iis is ercd it 'mtoa jserwce chamber at one side of the piston," and an -actuator chamber separate therefrom on the other. side of the piston, saldservice chamber being provided with a liquid passage tor connecting. it, to'a hydrauiic'brak eactuating cylinder, a liquid essure pump, 'a connection from the ressure side of sa1d. pump to said actuator 9 amher, a connection from the suctlon side of .said pump to said actuator chamber, valves for controlling said connections 'an operator operated. devices connected with said valves,

- and capable of holding said valves in open connection with position to permit a continuous circulation of liquid through 7 said connections and to close one or other of said valves to efiect a deli ery of pressure liquid into, or a dischar e of pressure liquid from said actuator c amber, a liquid reservoir,-a connection therefrom to the suction side, of the pump for supplying the pump when the suction the actuator chamber is closed, a connection from the reservoir to the pressure side of the pump to permit the chamber, and equalize the "therein with that in the'actuator vc arnber.

the connection from-the pumpto the actuator is closed, and automatic valves controlling said reservoir connections, said ac-.

tuator piston being provided with a passage 'ther'ethrough for establishing" communica- 25 In testimony whereof we afiix our signa- I t CALEB S.BRAGG. j .v

. vrg'ron w. QKLIESRATHL to discharge liquid into saidreservoii' 0 chamber exceeds that in the service 

